This invention pertains to a telephone system including centrally located telephone answering equipment, and more particularly to such a system in which a subscriber may access his assigned telephone answering device through calling a telephone number assigned to a tone generator, also centrally located, the operation of which establishes an operative connection between the device and the subscriber.
There are various telephone answering services now made available by telephone companies in which a plurality of telephone answering devices is located at the company's central office, which devices are leased or rented by various subscribers. In other words, instead of a subscriber having his own answering device located at the place of his office or home telephone, he rents the use of such a device which is under the maintenance and control of a telephone company.
One of the problems in the past has concerned the provision for the subscriber to gain access to his assigned answering device for the purpose of changing an outgoing message, listening to incoming messages, etc. One type of prior art system has made use of so-called pocket tone encoders, which are small battery-powered hand-held devices about the size of a package of cigarettes, with these devices including keys or pushbuttons for generating tone codes that are used to gain access to a remote answering device. These hand-held devices, however, are sometimes inconvenient to carry, or may be forgotten, and can be quite expensive. Another prior access system has involved the use, in a conventional tone-dial telephone system, of the two so-called "special" tone-dial buttons which are provided in the system and which carry no number or letter designations. While it is possible in certain areas to arrange with a telephone company to use these two buttons, an important drawback here is that the company may, at some time in the future, decide to realign priorities for the use of these buttons, which realignment would result in the loss of accessing service.
A general object of the present invention, therefore, is to provide a novel and very simple and inexpensive system solving these accessing problems in a practical and satisfactory manner.
According to a preferred embodiment of the invention, a telephone system is provided which employs centrally located telephone answering devices, each assigned to a different subscriber's telephone line in accordance with the subscriber's wish to have central telephone answering service. Also centrally located in the system, and intended to be shared by all of the answering devices in the system, or at least by a large number of such devices, is an audio electrical tone generator which is assigned its own telephone line having its own distinct calling number.
Further included in the proposed system, and associated with each answering device in the system, is an audio tone sensor and special switching mechanism. Under normal circumstances, with respect to a particular subscriber's telephone line, this switching mechanism establishes a closed connection between the line and the telephone company's central office switching equipment, and also produces a normally open connection between the line and the appropriate input to the answering device circuitry. The switching mechanism is under the control of the audio tone sensor.
What a subscriber does to gain access to his assigned answering device is to dial or otherwise call the telephone number assigned to the shared tone generator. On the call arriving at the tone generator, the same turns on, and by virtue of the direct connection existing between the subscriber's line and tone generator, the tone generated by the generator is transmitted to the subscriber's line and picked up by the sensor. The sensor responds to this condition by actuating the switching mechanism so as to break the connection between the line and the central office switching equipment, and to make a connection between the line and the circuitry in the answering device. A subscriber may then in any suitable fashion, for example, in accordance with certain dial or tone codes, operate the answering device in any one or more of its several functioning modes. When the subscriber hangs up his phone, the switching mechanism is returned to its initial condition so that the open and closed connections mentioned above are reestablished.
A special feature herein is that means is also provided whereby during a time that a subscriber has access to his device, should an outside caller try to reach him, a distinctive tone sounds over the subscriber's line, letting him know that he has an incoming call. To receive this call, if he so wishes, he need simply hang up his phone and allow it to ring in the usual fashion. When he picks up the phone in answer to the ring he is properly connected to the calling party.
These and other objects and advantages which are attained by the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.